How bad of a year was 2013 for President Barack Obama? The economy is strengthening as he starts to wind down America's longest war, but his poll numbers are the lowest since he took office almost five years ago.

Usually, a growing economy and bringing the troops home mean public love for the commander in chief, but not this time.

The flush of success from Obama's re-election last year faded quickly as his administration faced a series of controversies -- some unavoidable and some self-inflicted -- that eroded Obama's credibility along with the belief that he can bring about the kind of change he called for in running for president.

"People don't think he's as competent as they used to think," said CNN Chief Political Analyst Gloria Borger. "They don't think he's as trustworthy as they used to think."

Here are six reasons for the President's difficult year, starting with his greatest achievement toward the promised change of his first term that became perhaps his biggest liability: the health care reforms known as Obamacare.

1)Obamacare blues

If one day in 2013 exemplified Obama's change in fortune from his first term, it was October 1.

On the same day, a highly unpopular government shutdown started because of Republican demands to dismantle Obamacare as part of a needed spending measure to keep federal agencies running.

It should have been a decisive double play for Democrats, with public anger at Republicans over the eventual 16-day shutdown rising as Americans finally got to experience the full benefits of the health care reforms they had been promised since the law was passed in 2010.

But the website malfunctioned badly from the start, with repeated stalling and error messages that made successful navigation impossible for most users.

Once the shutdown ended on October 16, media focus shifted to the full extent of the Obamacare website problems.

That gave Republicans fiercely opposed to the health care reforms a new opening to attack both the overall law and the big government approach of Democrats.

On top of all this came reports that insurers were sending cancellation notices to individual policy holders that undermined Obama's repeated pledge of previous years that "if you like your health care plan, you can keep it."

While less than 5% of the population, the individual health insurance market comprised several million people whose stories of canceled policies took over the media narrative. PolitiFact declared Obama's false promise its "lie of the year."

Now Republicans trying to dismantle the reforms warn of more hidden impacts including higher premiums and canceled coverage in the first full year of Obamacare in 2014.

"This really represents the single ... biggest instance of consumer fraud in the nation's history," GOP Sen. John Cornyn of Texas told reporters this week. "And the American people are increasingly led to the conclusion they cannot trust this administration to say what it means or mean what it says."

Obama brought in outside tech experts to get the website working better, and enrollment figures increased in November and December. However, it remained unclear if the administration can regain control of the narrative.

On Friday, the website was down again for a few hours, but Obama boasted to reporters at his year-end news conference that more than 1 million people had enrolled so far.

"It's crazy how this has switched, even given the fact that the Republicans blew the government shutdown like they did in October," Borger said.

Obama shrugged off the low poll numbers on Friday, telling reporters at his year-end news conference that "if I was interested in polling, I wouldn't have run for president."

Instead, he cited continuing economic growth after the recession he inherited when he took office in January 2009 and other progress such as the growing Obamacare enrollment.

"That is a big deal. That's why I ran for this office," Obama said.

His approval ratings started declining in most national surveys in June as he dealt with controversies such as IRS targeting of tea party groups seeking tax-exempt status and classified leaks that revealed National Security Agency surveillance of phone records.

"Many people assume that Obama's low approval ratings today are due to the flawed health care website that debuted in October," CNN Polling Director Keating Holland said Thursday. "But the biggest drop in Obama's numbers came in the late spring and early summer. In mid-May, Obama's approval rating was at 53%; by mid-June, after revelations about the IRS and the NSA, it had dropped to 45% and stayed there for several months."

Holland concluded: "It's been a bad year for Obama, but his troubles didn't start in October -- they date back to May and June."

3)Snowden leaks

The Patriot Act passed after the 9/11 attacks led to a huge NSA surveillance network that operated under review by secret courts, with little public knowledge.

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Then former NSA contractor Edward Snowden leaked a trove of classified documents about it in June.

Suddenly, a program Obama inherited became a major problem, as Snowden's revelations showed the government routinely collected phone records -- but not the content of calls -- for possible use in tracking terrorism suspects.

Suspicions that the government spied on its own people ensued, fueled by incomplete or misleading administration responses such as when Director of National Intelligence James Clapper denied to a congressional committee that such surveillance occurred.

Snowden's leaks also made public embarrassing revelations of U.S. spying on allies such as Brazil, France, Mexico and Germany.

While Obama never personally bore the brunt of direct responsibility for the extent of the NSA surveillance, the Snowden leaks enhanced a public perception of an administration steeped in secret activities that it denied or tried to continue hiding.

The issue caused rifts in Obama's Democratic base, with liberals opposed to the surveillance that the President defended as important for national security.

He also has angered the liberal wing by continuing the policy of his immediate predecessor, Republican President George W. Bush, to use drone strikes against terrorism targets abroad.

4)IRS targeting

An inspector general's report in May that showed the IRS targeted conservative groups in determining extra scrutiny of applications for tax-exempt status was the scandal du jour in Washington before being relegated to back-burner status by the Snowden leaks.

An internal investigation found no evidence of anti-conservative conspiracy, and officials eventually determined that IRS employeesalso used terms referring to liberal or progressive groups in their screening.

Regardless of the outcome, the IRS controversy bolstered Republican efforts to portray the administration as willing to push a partisan agenda to the edge of legal limits and perhaps beyond.

5)Stalled agenda

CNN Chief National Correspondent John King called Obama "0 for-2013" in terms of what he proposed in his State of the Union Address in February with what got passed by Congress.

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No immigration reform. No jobs program. No tax reform. No increase in the minimum wage. No expanded background checks on gun purchases in the wake of the Newtown school massacre despite a major push by the President.

Obama and Democrats blame Republicans for obstructing possible progress in a divided government with different parties controlling the House and Senate.

"This last year has been totally obstructed. Everything we've tried to do, we have been stopped," Senate Majority Leader Harry Reid complained on Thursday.

Republicans contend it was Obama who prevented progress by refusing to seriously consider their positions or concerns, accusing him of a "my way or the highway" approach.

The partisan impasse was most evident in the repeated showdowns over federal spending that culminated in the October shutdown.

Conservative Republicans got the most blame for the shutdown because of their failed effort to tie the budget negotiations to dismantling Obamacare.

But polls showed public anger at everyone over the brinkmanship that economists said hindered the nation's slow but steady economic growth.

A budget compromise worked out after the shutdown amounted to rare bipartisan cooperation on spending issues.

The House and Senate easily passed the two-year spending framework that puts off further shutdowns over the budget until after next year's congressional elections, and Obama has signaled he will sign it.

"It's probably too early to declare an outbreak of bipartisanship, but it's also fair to say that we're not condemned to endless gridlock" that led to the government shutdown in October, Obama said on Friday.

The question is whether election year politics will bring the usual hardening of partisan positions, or if legislators believe further compromise will boost their standing with voters.

Obama called for Congress to make 2014 a "year of action" on issues such as immigration reform, job creation and expanding background checks on gun buyers.

However, he refused to budge in his rejection of Republican calls for concessions in return for their agreement to increase the federal borrowing limit -- known as the debt ceiling -- when required as soon as early March.

6) Reality versus perception

What do you remember about Obama's speech at Nelson Mandela's funeral?

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For most people, the answer will be the interpreter accused of making up sign language, or Obama huddling with the Danish and British prime ministers for an apparent "selfie" photo, rather than anything the President said.

He isn't the first President to be trivialized by the media and joked about on late-night talk shows, but coupled with the endless Republican attacks and low poll numbers, the perception of Obama has changed dramatically from the freshly re-elected leader praised for a dynamic inauguration speech last January.

Critics enjoyed skewering him over a series of diplomatic jabs scored by Russian President Vladimir Putin, who ignored a U.S. request to return classified leaker Snowden to face prosecution and intervened diplomatically in Syria after Obama failed to muster an international force to punish the Syrian regime for crossing his "red line" on using chemical weapons.

In the end, though, Obama appeared to get what he wanted without putting any U.S. troops at risk, as Syria -- under pressure from ally Russia -- handed over control of its known chemical weapons arsenal to the international community.

A bad year for sure, but not the death knell of his presidency.

"Can he turn it around? Sure he can," CNN Political Commentator Ryan Lizza said. "I think his fortunes will be about the improving economy, and there's a lot of good economic news coming out right now and 2014-2015. If the economy turns around, those (poll) numbers that we saw will turn around."